Piston skirt expander



March 20, 1934.

R. w. PATON 1,951,837

P ISTON SKIRT EXPANDER Filed April 12, 1935 Patented Mar. 20, 1934 UNITED STATES PATENT OFFICE PISTON SKIRT EXPANDER Application April 12, 1933, Serial No. 665,727

12 Claims.

My invention relates to means for expanding the split skirt of a piston.

One of the objects of my invention is to provide an improved expander for maintaining the split skirt of a piston of an internal combustion en ginc and the like in proper engagement with the cylinder wall.

Another object of my invention is to prevent play between the piston pin bosses and invar struts of the invar strut type of piston.

With the above and incidental objects in view the invention consists in certain novel features of construction and combination of parts, the essential elements whereof are recited in the w appended claims and two forms of embodiment of which are described in detail hereinafter and illustrated in full in the accompanying drawing which forms part of this specification.

Fig. 1 is a bottom plan view of a piston having one form of my improved device applied thereto;

Fig. 2 is a reduced side view of the piston partly broken away to show part of the expander in position within the piston;

Fig. 3 is a reduced side view taken at 90 of Fig. 2;

Fig. d is a side view of the main expander shown in Fig. 1;

Fig. 5 is a perspective view of the spring brace which, in effect, forms a part of the main expander and serves to prevent play between the piston pin bosses and struts, and

Fig. 6 is a perspective view of a modified form of my invention.

Referring first to Figsmlg 2 and 3, the piston a shown in these figures for illustrative purposes is of the invar strut type. The piston is preferably formed of aluminum alloy and comprises a head 7, a skirt 8 consisting of cross head slippers 9 and a lower circular guide portion 10, and webs piston pin bosses 12, the webs being connected below the bosses to the circular portion 10 by integral portions 13 and to the side edges of the.

11 depending from the head and provided with.

19 of the strip curved toward and contacting each other as best illustrated in Fig. 1. A recess 20 (Fig. 4) is formed in each free end, providing, in effect, two tongues. The strip has an elongated opening 21 forming two parallel portions 21. The sides of the expander between the recesses 20 and opening 21 are provided with holes 22 through which a piston pin 23 is adapted to project. The central parts of portions 21 are bowed or curved inwardly to increase the expansive action. The sides of the expander on either side of the holes 22 are provided with vertical expansion ribs 24.

Fig. 5 shows an auxiliary expander or spring brace 25 which is also formed from a strip of spring steel. It is bent to give it a U-shape with the central portion 26 curved or bowed inwardly and the free ends 25 curled or turned inwardly. The centralcurved portion 26 is of such width as to fit snugly in the central part of the opening 21, that is to say, between the curved parts of the portions 21* of the main expander.

It will be understood that the expanding device is contracted by hand or any suitable means when it is to be inserted in the piston skirt. When the expanding device has sprung into po sition in the piston skirt, the piston pin 23 is inserted through the openings 22. The portions 21 contact at 27 with the interior wall of the piston skirt opposite the vertical slot 15, the 35 curved tongues 19 contact with the interior wall of the skirt adjacent the vertical slot 15 and the fiat sides of the expander press in opposite directions against the facing edges of the bosses 12. The spring brace 25, which is inserted with the main expander, has its bowed part 26 in align ment with the bowed parts of the portion 21 and contacts with the skirt along the lines 27 and the free curled ends 25 fit in the angles between the bosses and struts 14 and firmlypress inwardly against the sides of the bosses and outwardly against the struts 14.

It will be seen that the expander 18 presses against the interior of the skirt at right angles to the piston pin bosses and against the ends of the bosses in opposite drection with the result that the expander expands the skirt and maintains it in expanded condition so that it snugly fits the cylinder walls, thus avoiding piston slap" and excessive blow-by and oil consumption. The spring brace 25 augments the main expander and is held in position by the latter. The main expander 18 may be provided with sharp lips 29 which bite.into the metal of the no skirt to lock the expander more firmly in position.

I have found that with the invar strut type of piston, there is a tendency of the invar struts 14 to loosen and permit movement or sliding in the webs or hangers 11 with the result that there is a rocking action between the skirt and the head. In forming the piston, the aluminum is poured into a mold in which the invar struts are mounted and the ends of the struts are supposed to be securely anchored in the side edges of the cross head slippers and the central portions of the struts are intended to be securely anchored in the webs or hangers 11. However, due to the differences in the coefiicient of expansion between the aluminum and the invar, there is quite often some play between theinvar struts and the aluminum hangers. To overcome this difficulty with this type of piston, I provide the spring brace 25 which prevents the sliding action, as the curled ends press firmly against the sides of the bosses and the struts 14 and takes out all play between the bosses and the invar struts.

In the modified form of my invention shown in Fig. 6, the spring brace is formed integral with the main expander, the spring arms 28 being struck out from the body of the main expander itself as shown in this figure.

It is apparent that further modifications and changes may be indulged in without departing from the scope of my invention.

I claim:

1. The combination with a piston having a split skirt and piston pin bosses, of a spring expander adapted to press against the facing edges of said bosses and at points on the skirt intermediate said bosses, the expander also having portions pressing against the sides of the bosses.

2. The combination with a piston having a split skirt, piston pin bosses and struts, of a spring expander extending across the skirt and contacting with the interior of the skirt on opposite sides, the expander also including tongues abutting and pressing against the sides of the bosses and against said struts.

3. The combination with a piston having a split skirt and piston pin bosses, of a spring expander polygonal in shape and engaging and pressing against the facing edges of the bosses and at spaced points on the skirt intermediate the bosses, and curled portions on the expander abutting against the sides of said bosses.

4. The combination with a piston having a split skirt, piston pin bosses and struts associated with said bosses, of a spring expander polygonal in shape and pressing against the facing edges of the bosses and at points on the skirt between the bosses, the expander having tongues abutting against the sides of said bosses and pressing against said struts.

5. The combination with a piston having a.

head and a split skirt, hangers connecting the head and skirt and having piston pin bosses, and struts having a smaller coefiicient of expansion than the skirt and hangers and connecting the skirt and hangers, of a spring expander extending across the skirt and contacting with the skirt on opposite sides and spring means associated with said expander for contacting the skirt on one side and preventing play between said struts and hangers.

6. The combination with a piston having a split skirt and piston pin bosses, of a spring expander adapted to press against the facing edges of said bosses and at points on the skirt intermediate said bosses, and a spring brace held in place by the expander and having portions pressing against the sides of the bosses.

'7. The combination with a piston having a split skirt, struts and piston pin bosses, of a leaf spring expander extending across the skirt and contacting with the interior of the skirt on opposite sides, and the expander having a recess, and a spring brace having a portion fitted in said recess and having its ends wedged against the sides of the bosses and the struts.

8. The combination with a piston having a skirt with a slot, piston pin bosses and struts, of a spring expander polygonal in shape and engaging and pressing against the opposite sides of the skirt intermediate the bosses, and a spring brace associated with said expander and having a central portion engaging the skirt opposite said slot and having its ends tightly wedged between the bosses and struts.

9. The combination with a piston having a split skirt, piston pin bosses and a piston pin, of a spring expander polygonal in shape and pressing against the facing edges of the bosses and at points on the skirt between the bosses, the expander having integral struck-out tongues abutting against the sides of said bosses.

10. The combination with a piston having a head, a split skirt, hangers connecting the head and skirt and carrying piston pin bosses, and struts having a smaller coefficient of expansion than the skirt and hangers and connecting the skirt and hangers, of a leaf spring expander engaging the skirt at spaced points and pressing against the facing edges of the pin bosses and having portions preventing play between the struts and hangers.

11. The combination with a piston having a head, hangers depending from the head, struts on the hangers and a split skirt connected to the struts, of a spring expander formed of strip metal and polygonal in shape and having contacting ends, the ends of the expander being adapted to engage the skirt intermediate the bosses and the sides of the expander being adapted to press in opposite directions against the facing edges of the bosses, and tongue struck-out from the sides of the expander and having curled ends engaging and pressing against the sides of the bosses and the struts.

12. A piston skirt expander formed of spring metal and having a recess, and a spring brace having a portion fitting in the recess and having its ends projecting outwardly from the expander.

ROY W. PATON. 

